What are 3G Networks?

3G network refers to the communication network that uses the third-generation mobile communication technology of cellular mobile communication technology that supports high-speed data transmission. 3G network is a new generation mobile communication system that combines wireless communication with multimedia communication means such as the Internet.

3g network

3G Introduction

Third Generation

The main difference between 3G and 2G is the increase in the speed of transmitting sound and data. It can better achieve wireless roaming worldwide, and handle multiple media forms such as images, music, and video streaming. It provides web browsing,

China has formulated its own new standard, which is incompatible with foreign 3G. With a 3G license, it can operate

^[1] With the advent of 3G technology, operators are also researching corresponding 3G network configuration strategies to meet different levels of business needs. For network infrastructure investment, operators' business plans must also support these strategies. Therefore, for 3G networks, the most important thing is to find a practical and balanced relationship between capacity and coverage to provide competitive services.

2, 3G wireless access characteristics

In the transition from the familiar 2G network to the 3G network, the wireless network has ushered in many new challenges to its design and planning in order to meet the real multi-services:

(1) Highly complete air interface, which has high flexibility in carrying and multiplexing a large number of voice services, and in particular, fixed and variable-rate data services in the range from low to high speed, up to 2Mb / s , Can effectively carry IP services.

(2) Design cell coverage and services for multiple services with different capacity and QoS requirements. Due to the huge differences in wireless link overhead, it is necessary to be able to distinguish the quality of service and communication needs of different services.

(3) There is a complete set of well-designed wireless link layers to ensure that a high spectrum utilization rate can be achieved in a variety of working environments from macro cells to pico cells and indoors.

(4) In order to eventually provide higher wireless capacity, 3G networks must provide effective methods for multi-layer network operation to support micro cells and pico cells, and provide effective ways for proper flow between these layers.

(5) The possibility of coordinating the setting with the existing 2G base station in order to reduce the cost and overhead of establishing and maintaining the base station. At the same time, in order to enable these two systems to obtain a good price / performance ratio, a comprehensive method is needed to identify the coordinated operation of 3G and 2G networks from the perspective of multiple radio frequencies.

3. Differences between WCDMA wireless system and GSM system

Compared with 2G network optimization, there are some essential differences between WCDMA and GSM systems, and there are many differences in details:

(1) Soft handover overhead design. Soft handover is a unique feature of WCDMA systems. Observation shows that minimizing soft handover overhead is closely related to establishing a suitable cell range, which is completely different from GSM systems.

(2) The range and isolation of the community. Relatively speaking, this is more important in WCDMA than in 2G, because the frequency reuse factor of neighboring cells in WCDMA is 1, resulting in close coupling of mutual interference. Compared with GSM systems, WCDMA can "see" more different base stations / cells.

(3) Vulnerable to external interference. For example, interference leaked by other adjacent carriers or similar interference between different WCDMA cell layers. Moreover, although this problem is not unique to WCDMA, its importance has increased significantly. For example, when the operating bandwidth is 5MHz, a WCDMA carrier bandwidth will occupy 25% to 50% of the available bandwidth of the service provider. Compared with the 2G narrowband system, any residual interference entering the WCDMA carrier or reducing the sensitivity of the receiver will have a more serious impact on the quality of service.

4, WCDMA wireless system optimization content

Coverage and capacity are closely related in WCDMA networks. Increasing capacity will lead to reduced coverage, so its network performance is difficult to predict. Because the various services supported by the network have different characteristics, it is difficult to evaluate the system load and cell characteristics. This puts forward higher requirements for the initial design and optimization of the system.

4.1 Cover

(1) Downlink coverage

Define the Ec value and Ec / Io value under various environment types. If it cannot be achieved, it will be guaranteed by optimization.

RSCP> -85dBm, Ec / Io> -10dB

Different businesses will drop calls;

RSCP between -100dBm and -85dBm, Ec / Io between -15dB and -10dB

Guaranteed less than 64kb / s data rate services;

RSCP> -85dBm, Ec / Io> -10dB

Can support various types of business.

(2) Uplink coverage

The uplink uses the comparison of the mobile phone's transmit power with the maximum value to determine whether the coverage limit has been reached.

For CS, UE_MaxTxPower is 21dBm; for PS, UE_MaxTxPower is 24dBm.

4.2 Loss of Neighborhood

In the WCDMA system, because the lost neighboring cells cannot be added to the active set in time, interference will occur, causing downlink dropped calls and reduced uplink call quality.

CPICH: Ec> RxLevmin; Ec / Io> Ec / Iomin. (Ec / Io minimum recommended -16dB)

4.3 Pilot pollution

When multiple scrambling code information is received in a certain area and the downlink quality of the best serving cell is reduced, it is referred to as pilot pollution. The judgment conditions are:

CPICH_Ec> -100dBm, CPICH Ec / Io <-10dB

Increasing the power of the CPICH is one of the methods to increase the Ec value of the best service area. If pilot pollution is caused by overlapping cells, you need to adjust the antenna tilt.

4.4 Soft handoff area optimization

The purpose of soft handover area optimization is to limit the soft handover area in the system to a reasonable range. It is recommended to control the soft switching area at about 30%. Through the antenna adjustment and soft handover parameter optimization, the soft handover area can be optimized.